1. Field of the Invention
This invention relates to liquid and solid nitrogen fertilizers. More particularly, it relates to the use of low molecular weight alkanoic acids and alkanoate anions thereof to enhance the effect of nitrogen fertilizers in promoting the growth and productivity of plants.
2. Description of the Prior Art
Plants require a variety of materials for adequate nutrition. The principal materials are carbon dioxide and water, which provide the elements of carbon, hydrogen and oxygen, and which are usually available in adequate amounts from both soil and atmosphere. The supply of carbon dioxide and water is continually replenished by natural phenomena. All the other essential nutrients are normally available from the soil, but they are not replenished by nature after the plant takes them up into its foliage and fruit. When the plant is removed from the soil for consumption, in contrast to the natural cycle of return to the soil, the soil nutrient supply is reduced, and the application of fertilizer becomes necessary in time.
Thirteen elements, which are normally drawn from the soil, are currently known to be essential to plant nutrition. These elements consist of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, iron, manganese, copper, zinc, boron, molybdenum and chlorine. Of these thirteen elements, nitrogen, phosphorus and potassium are needed by the plant in relatively large quantities and are therefore called macronutrients. Calcium, magnesium, and sulfur are generally required in lesser but still substantial amounts and are classified as secondary nutrients. The remaining members of the group are known as micronutrients since they are required in very small amounts for plant growth.
Although carbon, hydrogen, and oxygen are known to be essential elements for plant growth and development, organic matter which contains only these elements is not generally recognized as having any direct role in plant nutrition. The soil organic matter, or humus, is known only to be of importance relative to soil texture and structure, serving to determine the reaction of the soil to air supply, water supply and retention of available nutrients. Except for nitrogen containing compounds such as urea, and a variety of chelating agents such as citric acid, specific organic compounds do not appear to have been suggested for use in the improvement of plant nutrition. The role of these chelating agents is to solubilize and maintain metals in a form which can be utilized by growing plants.
U.S. Pat. Nos. 3,909,229; 3,997,319; and 3,854,923 are directed to a micronutrient composition consisting of a solution in anhydrous or aqueous ammonia of a zinc alkanoate which contains from 1 to 6 carbon atoms, and zinc acetate is identified as being a suitable zinc alkanoate. These patents teach that the zinc salts of low molecular weight alkanoic acids are desirable sources of zinc for use in combination with ammonia as a consequence of their relatively high solubility in aqueous or anhydrous ammonia. These patents do not, however, suggest the possibility that low molecular weight alkanoic acids and alkanoate anions thereof could have any desirable effect on plant nutrition which is independent of the presence or absence of zinc.
Similarly, U.S. Pat. No. 4,007,029 discloses the preparation and use of a liquid fertilizer composition which comprises anhydrous ammonia, at least one trace element selected from the group consisting of boron, copper, magnesium, manganese and molybdenum, and wherein a compound such as ammonium acetate, magnesium acetate or sodium acetate may be used to solubilize the trace element. This patent fails to suggest that acetate anion could have any desirable effect on plant nutrition which is independent of a trace element.